As a small thread drift, if Ham Standard hollow steel props had problems, you should have seen the Ham Standard hollow dural blades on the Lockheed L-1649. Heard a crowd outside our maintenance office at the JFK IAB. An Air France L-1649 had parked outside our door. L-1649 had slower turning props than the L-1049's and so had wider chord prop blades which, to save weight, were new type hollow aluminum.
The Nbr. 3 prop had one blade that had split open down the leading edge. Some internal foam stuffing was sticking out. Pretty quickly the hollow dural blades were replaced by solid dural blades.
Hollow steel blades were a specialty of Curtiss Electric props and Aeroproducts as pointed out. From a line maintenance point of view the blades caused us little trouble.